MV POWER CAPACITORS AND BANKS

2014
MV POWER CAPACITORS AND BANKS
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QUALITY MADE IN ITALY
Index
Icar: Products and solutions
1
ICAR Quality System
3
Medium and High Voltage Solutions
3
Capacitors
BIORIPHASO/TF
BIORIPHASO/TF Without internal fuses
BIORIPHASO/TF With internal fuses
BIORIPHASO/TF trifase / three phase
4
7
9
11
Capacitor Bank
12
Metal Enclosed Capacitor Banks
14
Technical Remarks
15
Safety and Storage Instructions
16
III
Icar: Products and solutions
ICAR is a leading manufacturer of capacitors and power factor correction systems in low and medium voltage; it controls with its
own companies all production phases: the polypropylene/paper film, metallization, winding,manufacturing of the finished product.
The ICAR Group has several plants, all located in Europe. The power factor correction range is made entirely in Italy.
For details on the individual families, download the full catalogs on the website, www.icar.com. Here are all equipment and the
solutions ICAR proposes.
1
Custom components
for power factor
correction
MV Capacitors and
banks for power factor
correction
Power electronics
capacitors
Active Harmonic
Filters
LV voltage
stabilizers
EMI RFI filters
Motor run
capacitors
Capacitors for
energy storage
and discharge
Lighting
capacitors
Isolation and LV/LV
special transformers
ICAR Means Capacitors
ICAR SpA is synonym of capacitor from 1946,
conjugated over its multiple applications.
All along ICAR has been believing in the quality
of its products and in the strength of the
International regulations for the achievements
of the high performance standards required for
capacitor in industrial applications.
Nowadays ICAR is one of the few companies
able to manufacture capacitors starting from
the raw material up to the finished product; the
entire process is checked in order to obtain a
product of high quality level that guarantees its
functioning even in the most burdensome plant
configurations.
Today ICAR produces different type of capacitors,
from the lighting and single phase motor types to
the ones for power electronics (electric traction,
industrial services) and those of medium voltage.
The various characteristics demanded to these
products in terms of electric, mechanical and
thermal stress, enabled to find technical solutions
that have been applying in other fields with
interesting results: for instance the optimization
of capacitors for special applications enabled to
find very strong solutions that have been then
applied on power factor correction capacitors.
The production of the dielectric film (polypropylene
or special paper), the metallization process, the
production of the capacitor and the construction
of the power factor correction banks are fully
executed within companies of the Group; that
guarantees the achievement of the highest
quality standard weather of the metalized film or,
consequently, the capacitors manufactured.
Furthermore, the know how acquired in almost 50
years of metalized film production, has enabled
ICAR to realize absolute innovative products like
3Ut range of capacitors.
Used to deal with International markets ICAR
faced the requests of the most strict Certification Bodies and was awarded UNI EN ISO 9001: 2008 Certification.
ICAR periodically takes part to CEI (Italian Ectrotechnical Commission) for the compilation of the product regulations, aimed at
setting the objective criterions to evaluate capacitors performances and safety.
It’s constantly in the vanguard and able to anticipate the regulations requirements; in order to ensure the accordance with the
International regulations and the most strict customers acceptance criterions, products are submitted to tests in the internal
laboratories (where it’s possible to test capacitors up to 700 э F and voltage up to 80 kV) and in the greatest internationally
recognized vanguard laboratories (CESI). Everything is performed for the safety of the customer who entrusted a reliable partner
with a pluridecennal experience in capacitors
2
Medium and High Voltage Solutions
ICAR offers numerous solutions for power-factor correction
and filtering of harmonics in Medium and High Voltage:
SINGLE PHASE CAPACITORS
• unit power up to 800kvar
• nominal voltages up to 36kV
• frequency of 50 or 60Hz
THREE-PHASE CAPACITORS
• nominal unit power up to 600kvar
• nominal voltages up to 24kV
• frequency of 50 or 60Hz
SPECIAL CAPACITORS FOR CUSTOMIZED
APPLICATIONS, SUCH AS FOR EXAMPLE
• three-phase with neutral brought out
• split-phase capacitor
• for overvoltage protection (typically used in
protection of large electrical machines)
• for applications in environments with abnormal
characteristics (such as high or very low temperature,
salty atmosphere, altitude above 1000 m, etc.)
MV AND HV POWER-FACTOR CORRECTION BANKS
• powers up to 100Mvar
• voltages up to 220kV
• frequency of 50 or 60Hz
3
TUNED CAPACITOR BANKS
• Tuned on harmonics from the 2nd to the 13 th
• power up to 100Mvar
• voltage up to 150kV
• frequency of 50 or 60Hz
MV AND HV SPECIAL FILTERS
Such as high pass, second order filters with double tuning
frequency, damping resistor, etc.
ICAR has over 60 years experience supply of products to
industries characterized by complex power factor correction
and harmonic filtering situations (steel mills, paper mills,
forging, cement factories) around the world (Saudi Arabia,
Russia, Hong Kong, China, Greece, France, Argentina,
Brazil, etc.). ICAR solutions are proven of effectiveness,
robustness and high reliability.
BIORIPHASO/TF MV Power Capacitors
GENERAL FEATURES
Capacitors of the BIORIPHASO/TF type series constitute
a complete range for making of solutions for power-factor
correction in MV and HV.
They are designed and manufactured using the most
modern technologies: ensuring long expected life and high
reliability. The BIORIPHASO/TF series is in compliance with
applicable standards (IEC 60871, ANSI, IEEE 18, NEMA
CP-1, etc.): they are therefore suitable for installation in
any environment or conditions described in the above
standards.
On request, we can, nevertheless, provide capacitors
with special characteristic or tested as specified by the
customer.
CLASSIFICATION
The various models are identified by
• series name
• power
• voltage
• typology
• single-phase: with or without internal fuses, with
single or double isolator;
• three-phase: with delta or star connection with
neutral brought out
EXAMPLE
BIORIPHASO/TF 200/12:
single-phase capacitor of 200kvar at 12kV
BIORIPHASO/TF 200/12/T:
three-phase capacitor of 200kvar at 12kV
All capacitors are uniquely identified by the relevant plate
as required by the IEC Standard 60871-1:
• Name of manufacturer
• Serial number/year
• Nominal power
• Nominal voltage
• Nominal frequency
• Temperature category
• Insulation level
• Internal discharge device
• Connection symbol
• 5HTLVM[OLPTWYLNUH[PUNÅ\PK
• Indication of the presence of internal fuses (if included)
/
DIELECTRIC
Dielectric and electrodes constitute the most important
parts of the capacitor, which determines the electrical
characteristics (capacity, losses) and affects the durability
and reliability over the time.
The dielectric of BIORIPHASO/TF capacitors is of the all
film type, that is, it is composed of several layers of rough
BOPP film (Biaxial Oriented Polypropylene) of very high
quality.
ICAR has its own factory of BOPP for capacitors that allows
to have complete control of the production chain.
ALUMINIUM ELECTRODES
The electrodes of BIORIPHASO/TF capacitors are made
of a thin sheet of purest aluminium to ensure the best
performance and greatest reliability.
The winding with the extended foils provides high withstand
capacity at current peaks consequent to the transients of
the capacitors switching or during the transients relating
to network fluctuations. The folded edge ensures a better
distribution of the electric field in these regions, providing
the capacitors with higher resistance to overvoltage and to
prevent the partial discharges.
IMPREGNATION OIL
BIORIPHASO/TF capacitors are vacuum impregnated with
dielectric fluid and are sealed without an air head.
The oil impregnates all the individual capacitive elements of
which the capacitor is composed, and it fills the entire free
volume, ensuring perfect isolation and absence of partial
discharges.
BIORIPHASO/TF 200/12/E:
as above, but with only one bushing
BIORIPHASO/TF
CAPACITOR CONSTRUCTION
Special attention is paid to the various stages of treatment.
Drying is carried out with the capacitor placed in a vacuum
autoclave at a high temperature.
At the end of the drying process, the interior of the
capacitors reaches the molecular vacuum.
BIOIL® is used for the impregnation of BIORIPHASO/TF
capacitors: it is a biodegradable, environmentally friendly
synthetic oil (free of PCBs and other substances harmful
to the environment) and it is non-toxic. The high quality
oil, produced by leading chemical companies, is further
refined at ICAR through vacuum degasification chemical
purification. Rigorous controls of its physical and chemical
properties are made prior to impregnation.
/
E
if single phase: with one bushing
FI
with internal fuses
T
three phase
rated voltage, in kV
rated power, in kvar. If Power is shown in two
addends, capacitors is split phase type.
4
DIELECTRIC LOSSES AND TOTAL LOSSES
Dielectric losses in BIORIPHASO/TF are very low, initially
below 0.07 W/kvar, reducing in less than 100 hours of work
to a value in the range between 0.02 to 0.04W/kvar.
Dielectric losses must be added to those of the discharge
resistances built into the capacitors.
BIORIPHASO/TF total losses, dielectric losses + loss of
discharge resistance are:
• less than 0.13 W/kvar for models with discharge
resistance designed to ensure a residual voltage less
than at 75V within 10 minutes (IEC standards)
• less than 0.18 W/kvar for models with discharge
resistance designed to ensure a residual voltage less
than 50 V within 5 minutes (IEEE standards).
HOUSING
The hermetically sealed housing protects the active part
(electrodes and dielectric), ensuring preservation and good
function over time.
The housing of BIORIPHASO/TF capacitors is made of
AISI 409 stainless steel sheet, very thick, bent and T.I.G.
welded. The completely automated process guarantees
the highest welding quality and thus the robustness and
hermetic sealing of the capacitor.
The elasticity of the larger surfaces of the housing ensures
that it follows the thermal expansion of oil due to the
variation of room temperatures.
At low temperatures the elasticity of the housing must
ensure that there will not be an inner depression that
reduces the dielectric strength of the oil and the voltage of
partial discharges.
At high temperatures, conversely, the elasticity of the
housing must ensure that the internal overpressure be
limited. The housing is protected with two layers of
synthetic paint suitable for outdoor service and having a
high mechanical strength and excellent performance in an
environment polluted by industrial fumes and fog.
The blue-gray colour, RAL 7031, allows for efficient
transmission heat within the environment.
For applications exposed to high solar radiation, a lighter
gray colour, RAL 7035, is used which provides for an
increased reflection of solar radiation, limiting internal
overheating.
The housing also has two handles for lifting and fixing the
capacitor. For specific needs, the positioning of the handles
can be changed on request, or additional handles can be
included.
5
BUSHING
The bushing of the BIORIPHASO/TF capacitors are made
of the highest quality porcelain, brown in colour; for large
lots, it is possible to provide bushing in a light gray colour,
upon request.
The porcelain bushings have a high resistance to electrical
arcs and to tracking (especially dangerous in highly polluted
industrial environments); they are resistant to chemicals,
atmospheric agents, heat, fungi and bacteria and are
mechanically very robust.
The porcelain bushings are, therefore, a quality choice for
BIORIPHASO/TF capacitors.
Before assembling, all the bushings are subjected to strict
controls.
The bushings of standardized models are suitable for
installation in places with moderate fog or industrial fumes.
For exceptionally polluted (salty or desert-like environments),
special bushings are provided with creepage distance of up
to 31 mm/kV.
The BIORIPHASO/TF capacitors are supplied with 1 or 2
bushing; the three-phase version are with 3 bushings or 4
(in the latter case, the internal connection of the capacitor
is star with neutral brought out).
DISCHARGE RESISTANCE
When the capacitors are disconnected from the network,
they remain charged, and the stored energy would be fatal
in case of accidental contact, so the power-factor correction
capacitors have an incorporated discharge resistor which
ensures capacitor discharge in a fixed time.
In accordance with IEC standards, the incorporated
discharge resistor in BIORIFASO/TF series ensures a
reduction of the residual voltage to 75V in less than 10
minutes.
On request, in accordance with IEEE standards, discharge
resistance at 50V in less than 5 minutes can be provided.
Important Safety Notice
Notwithstanding the presence of the discharge resistor, it
is mandatory to short circuit and earthing terminals of the
capacitors before any possible contact or handling.
Capacitors shall be also stored with short circuited
terminals.
ROUTINE TESTS, TYPE TEST AND SPECIAL TEST
ICAR subjects all BIORIPHASO/TF capacitors to all routine
tests required by IEC standards 60871 and it issues
relevant certificates.
The HV laboratory of ICAR is equipped to perform all
routine tests, type tests and the special tests as foreseen
for by IEC 60871.
࡛Routine tests:
Capacitance measurement (IEC 60871-1, art. 7)
4LHZ\YLTLU[VM[OL[HUNLU[VM[OLSVZZHUNSL[HUхVM[LZ[
capacitor (IEC 60871-1, art. 8)
Voltage test between terminals (IEC 60871-1, art. 9)
AC voltage test between terminals and container (IEC
60871-1, art. 10)
Test of internal discharge device (IEC 60871-1, art. 11)
Sealing test (IEC 60871-1, art. 12)
Discharge test on internal fuses (IEC 60871-4, art 5.1.1)
࡛Type Test
Thermal stability test (IEC 60871-1, art. 13)
4LHZ\YLTLU[VM[OL[HUNLU[VM[OLSVZZHUNSL[HUхVM[OL
capacitor at elevated temperature (IEC 60871-1, art. 14)
AC voltage test between terminals and container (IEC
60871-1, art. 15)
Lightning impulse voltage test between terminals and
container (IEC 60871-1, art. 16)
Short circuit discharge test (IEC 60871-1, art. 17)
Disconnecting test on internal fuses (IEC 60871-4, art. 5.3)
࡛Special tests
Ageing test (IEC 60871-2, art. 2.1.4)
Overvoltage cycling test (IEC 60871-2, art. 2.1.3).
6
BIORIPHASO/TF
Single Phase
ICAR makes two types of single phase capacitors:
• without internal fuses
• with internal fuses.
MV capacitors are internally made by connecting in series a
number of parallel element groups (see picture 1).
In the capacitors with internal fuses, there is a fuse in series
to each element which melts and isolates the same in case
of dielectric perforation: so capacitors can keep on service
with a small output reduction (see picture 1).
In case of capacitors without internal fuses the element
perforation short circuits the entire series group at which it
belongs, and the capacitors keep on service with an inner
fault.
The choice of capacitors types depends on bank designer
choice and on its power and rated voltage.
BIORIPHASO/TF SINGLE PHASE
WITHOUT INTERNAL FUSES
Small capacitors banks (up to 600 kvar) are made with
single phase capacitors without internal fuses, they are
connected in delta and protected by means of HRC limiting
current fuses.
Capacitors banks of higher power (from 600kvar to
1500kvar) are made up of at least six single phase
capacitors or three split-phase, without internal fuses, with
capacitor bank connected in insulated double star and
unbalance protection.
In case of capacitors without internal fuses, higher power
capacitor banks use one single external expulsion fuse
for each capacitor; this fuse, which is specific for power
capacitors, is very easy and effective, and it allows an
immediate evidence of faulty capacitor.
In these type of banks the number of capacitors is chosen
so to allow the bank to keep on service even in the case
one capacitor has been insulated by its fuse melting.
An unbalance protection, which works out a lower priority
protection, will provide the capacitor bank disconnection
after a certain number of capacitors are out of order.
Capacitors without internal fuses, which have smaller
losses than those with internal fuses, are designed to lower
dielectric withstand and are so much more robust and
reliable.
Picture 1
Single phase without internal fuses capacitors are made in
units of power ranging from 50 to 500 kvar, and with rated
voltage from 1.5 kV to 25 kV.
Picture 2
7
Power
(kvar)
Voltage
(kV)
Dimensions (mm)
L
P
H
Bushing
N
M
Weight
kg
350
140
180
170
100
14
100
4.16/©3 - 4.16
6.6/©3 -6.6
350
140
270
100
100
21
150
10/©3
350
175
310
140
100
29
200
10.5/©3
350
175
380
140
100
34
200
165
39
50
up to
75 kV BIL
180
up to
125 kV BIL
318
250
11/©3
15/©3
350
190
420
300
20/©3
22/©3
350
190
490
200
165
47
400
30/©3
33/©3
350
190
620
200
165
57
350
190
760
200
165
71
500
OPERATING CONDITIONS
• Temperature class -40/B
• Use: indoor/outdoor
• Altitude a.s.l.: 1000 m
• Frequency: 50/60 Hz
INSULATING VOLTAGES
Highest system
Voltage
(kV)
Short time withstand
voltage
(kV)
Lighting impulse
voltage test
(kV)
3.6
10
40
7.2
20
60
12
28
75
17.5
38
95
24
50
125
180
318
BUSHINGS
• Voltage levels: 12/28/75 kV
• Creepage distance > 255 mm
• Voltage levels: 24/50/125 kV
• Creepage distance > 600 mm
• Other voltages and powers available upon request
BIL 75 kV
BIL 125 kV
8
BIORIPHASO/TF SINGLE PHASE
WITH INTERNAL FUSES
As mentioned earlier in these capacitors each capacitive element inside the capacitor has an internal fuse in series (see picture 2).
In the event that an element has a fault, the fuse intervenes to exclude the damaged element, without removing the parallel elements
from service.
The break of the fuse is very fast (tens of milliseconds) due to energy stored in parallel elements.
Doing so other protection can’t operate and capacitor can stay in service with a small capacitance reduction.
The high reliability of these solutions allows to design capacitors with an higher dielectric stress and so units of reduced volume and
higher reactive power per volume unity.
ICAR available capacitor range which can be equipped with internal fuses is shown in Table 2 (blue zone).
It is clear that small power capacitors and those of high voltage are excluded.
The reason of this choice are strictly related to the criterion of good design of these type of capacitors and they are briefly described
below.
A well made design of internally fused capacitors requires indeed that each series group stored energy, while the sinusoidal voltage
reaches its peak value, is sufficient to assure an immediate fusion of the fuses in the even of one element fault.
With a lower stored energy the fusion time would be uncertain, it would indeed happen for the capacitor current and within a time
equal to several cycles of the fundamental frequency.
Each element disconnection due to its fuse melting, causes a voltage increase across the other elements of the same series group.
This voltage increase is in reverse proportion to the number of group elements.
A good internally fused capacitor design requires that the number of parallel elements is chosen to limit such rise: it is necessary at
least 10 elements to ensure the voltage rise is less than 10%.
Usually the series group parallel elements are not less than 14-16.
Series group stored energy limitations and minimum number of parallel elements, along with the limitations voltage per element, lead
to make not convenient to make internally fused capacitors of small power and high voltage or big power and low voltage.
Power
Voltage
V
Q
100-150 kvar
150-200 kvar
200-250 kvar
250-300 kvar
300-350 kvar
350-400 kvar
400-450 kvar
450-500 kvar
500-550 kvar
550-600 kvar
Table 2
9
1.9 kV
2.4 kV
3.8 kV
4 kV
5.7 kV
6.1 kV
6.6 kV
8.66 kV
11.5 kV
Power
(kvar)
Voltage
(kV)
400
Dimensions (mm)
P
H
HB Bushing
N
M
Kg
350
175
720
up to
75 kV BIL
180
200
100
60
200
165
73
200
165
83
300
165
94
300
165
106
500
4.16/©3 - 4.16
6.6/©3 -6.6
350
190
810
600
10/©3
10.5/©3
11/©3
350
190
930
700
15/©3
20/©3
350
190
1070
350
205
1100
800
Weight
L
up to
125 kV BIL
318
OPERATING CONDITIONS
• Temperature class -40/B
• Use: indoor/outdoor
• Altitude a.s.l.: 1000 m
• Frequency: 50/60 Hz
INSULATING VOLTAGES
Highest system
Voltage
(kV)
Short time withstand
voltage
(kV)
Lighting impulse
voltage test
(kV)
3.6
10
40
7.2
20
60
12
28
75
17.5
38
95
24
50
125
180
318
BUSHINGS
• Voltage levels: 12/28/75 kV
• Creepage distance > 255 mm
• Voltage levels: 24/50/125 kV
• Creepage distance > 600 mm
Other voltages and powers available upon request
BIL 75 kV
BIL 125 kV
10
Bioriphaso/TF Three-Phase
The three-phase capacitors are a simple and cheap solution to create groups of three-phase power factor up to 500 kvar.
They are normally used for power factor correction of motors or no load MV/LV transformers. Inside the three-phase capacitors are
composed of three single phase units connected in delta or star or star with neutral brought out.
The three-phase capacitors for voltages up to 12 kV are usually delta connected and protected with current-limiting type fuses (HRC fuses with
a high switching capacity). It’s important to use this type of fuses to prevent the explosion of the capacitor that in case of short circuit will absorb
the phase to phase short-circuit system current. Capacitors with internal star connection or with neutral brought out are provided on request.
Dimensions (mm)
Power
(kvar)
Voltage
(kV)
L
P
H
100
2,4
450
130
250
200
4.16
6.3
450
130
390
300
6.6
7.2
450
185
390
400
10
10.5
450
185
500
500
11
12
450
185
610
HB Bushing
up to 60 kV BIL
indoor 135
up to 75 kV BIL
indoor
outdoor 180
N
M
Weight
Kg
230
100
21
300
100
33
300
165
45
340
165
56
340
165
69
OPERATING CONDITIONS
• Temperature class -40/B
• Use: indoor/outdoor
• Altitude a.s.l.: 1000 m
• Frequency: 50/60 Hz
135
180
BUSHINGS
• indoor
• Voltage levels: 7.2/20/60 kV
• Creepage distance > 135 mm
• indoor/outdoor
• Voltage levels: 12/28/75 kV
• Creepage distance > 255 mm
Other voltages and powers available upon request
outdoor
BIL 75 kV
11
indoor
BIL 60 kV
Capacitor
Banks
ICAR proposes Medium Voltage capacitor banks by
assembling BIORIPHASO/TF capacitors along with other
components in order to make integrated and completed
solutions.
Capacitor banks can be suitable for indoor or outdoor
use, with damping reactors, tuned or detuned reactors for
harmonic blocking or absorption.
The most adopted scheme is double insulated star with
unbalance protection between the two stars; which allows
to spot a single capacitor fault.
The bank, depending on type of capacitor, could be also
equipped with the following protection means:
• Expulsion or HRC fuses
• Capacitor inner fuses
DAMPING REACTORS
Transient overcurrents of high amplitude and high frequency
may occur when capacitors are switched on and especially
when a step of a capacitor bank is switched in parallel with
other steps which are already energized.
The peak value of the inrush current should be limited to a
maximum of 100 times the r.m.s. value (see IEC 60871-1).
For MV or HV capacitor banks when the natural values of
the inductance of the network, in the case of a single bank,
or inductance between the batteries in the case of multiple
batteries in parallel, is not sufficient to limit the inrush
current, damping reactors are installed in series with the
capacitor banks that aim to limit this current.
The reactors are installed directly on the capacitor bank
and remain in service throughout the operating time of
capacitor banks.
The damping reactors are made of an air core, dry insulation
and winding copper or aluminum.
The design of the damping reactor must consider both, the
maximum continuous current as well as the inrush current
and its frequency.
An accurate assessment of the switching on transient
is necessary for the correct sizing of the reactor and its
internal insulation (insulation between turns).
Because the damping reactors are air core, during the
installation of the capacitor bank the isolation distances
and the magnetic distances from metal and from closed
turns must be respected.
HARMONIC DETUNED
AND TUNED FILTERS
DETUNED CAPACITOR BANKS
In case of capacitor banks to be installed inside harmonic
current polluted networks, which are generated by no linear
loads such as frequency converters, drivers a specific study
of the network impedance should be done at the point of
capacitor bank connection.
The switching of a capacitor bank can indeed trip
resonance phenomenon which amplifies harmonic currents
and generates overloads and higher distortions.
In the simpler case of a shunted capacitor bank, which
is in parallel to harmonic current generating loads, the
parallel resonance frequency between the capacitor bank
capacitance and the line inductance could be close to the
several harmonic current frequency and so to magnify them
and to over charge both the distribution transformer and
the capacitor bank itself, further than lead to a very high
distortion of the voltage waveform that could compromise
the proper working of all other electrical devices which are
wired to the same distribution system.
Whenever harmonic generating loads are a small part of
the whole and harmonic absorption filters are not required,
detuned capacitor banks are used; they are made up of
pure capacitor banks which are in series to properly sized
reactors to generate low pass filter having a detuning
frequency which is below the lower existing harmonic
current frequency.
This way the bank behaves as a pure capacitor below such
frequency and as a pure reactor above such frequency.
The resonance parallel frequency is so shifted below all nolinear loads generated harmonic current frequencies and
any amplification phenomenon is avoided.
While the detuned capacitor bank will be working at
a frequency above the blocking, it will turn to be as big
impedance and the load generated harmonic currents will
partially flow either on the mains or inside the capacitor
banks, depending on the specific frequency.
For capacitor bank power lower than 1-2 MVAR capacitor
bank absorbed harmonic currents are small, the higher the
capacitor bank reactive power the bigger the capacitor bank
absorbed harmonic currents is; for big banks the absorbed
fifth harmonic current by a 4,1 times the fundamental
detuned bank might reach as much as 40-50% of the no
linear load absorbed currents, which turns the detuned
filter a low efficiency absorption filter.
In MV networks the most common detuning frequency
is 4,1 times the 50Hz or 60Hz fundamental frequency
(XL%=6%), or seldom 3.8 (XL%=7%) or 2.8 (XL%=13%).
As far as small capacitor banks are concerned, iron multiair
gaps linearized core reactors are recommended.
On the contrary for higher power capacitor banks air core
reactors are more adequate.
At capacitor bank design a higher actual voltage level
shall be considered, this is for the series reactors voltage
increased effect and for the absorbed harmonic current
contribution (see IEC 60871-1 appendix B).
12
TUNED FILTERS
As far as harmonic generating loads are prevailing among
the others, typically in plants such as steel mills, arc
furnaces, it is likely that substantial current and voltage
harmonic pollution levels are flowing through the network,
and so it turns to be required to adopt harmonic absorption
filters to reduce such distortions and to compensate for the
most relevant harmonics.
MV harmonic absorption filters are of passive type, and
they are made by capacitor banks which are wired in series
to properly design reactor to create absorption targeted
harmonic resonance circuits.
Below the tuning frequency the filter capacitor bank behaves
as capacitor and it cater for power factor correction as
well. At the tuning frequency the capacitive reactance and
the inductive reactance are mutually compensated and the
cap bank impedance is made by the resistive part only, so it
becomes a low impendence path for the harmonic current
to be erased.
Above the tuning frequency the inductive reactance will
prevail and the filter will be an inductance.
Tuned harmonic filters shall always be tuned to the lower
harmonic current present, in other words, if the aim is to
reduce or erase a determined harmonic current, lower
frequency harmonics shall be compensated as well,
otherwise they would be amplified by the parallel resonance
between network impendence and filters of higher order.
For example if in a plant 5, 7, 11, 13 harmonic currents
are found, even if the 11th would be the most relevant, it
wouldn’t be enough to install 11th harmonic filter, but 5th
and 7th harmonic filter shall be there as well.
In special cases also attenuating filters and high pass filters
are used.
MV tuned filter reactors are generally air core and the most
disadvantageous and heavy harmonic conditions load shall
be considered at their design stage.
At capacitor bank design a higher actual voltage level
shall be considered, this is for the series reactors voltage
increased effect and for the absorbed harmonic current
contribution (see IEC 60871-1 appendix B).
13
UNBALANCE PROTECTION
Capacitor banks are usually protected by means of
unbalance protection which ensures the phase balance.
The most common protection scheme foresee an insulated
double star capacitor bank connection, where the two start
points are connected via an unbalance protection CT which
supplies secondary current to an homopolar over current
relay.
In normal working conditions star points are balanced and
no current flows into the CT. As soon as one capacitor
is faulty, its star becomes unbalanced and an unbalance
current flows into the CT.
In fact CT connection between the two star points, ensure
their equipontential status, hence if any of the two stars is
unbalanced a homopolar current is generates and it closes
the loop through the CT.
OPEN RACK BANKS
They are made of capacitors which are mounted on hot
deep galvanized steel rack; they are usually complete of
aluminum connecting banks, unbalance protection CT,
stacking insulators, damping resistors and expulsion fuses.
ICAR designs, manufactures and delivers complete open
rack banks suitable for network voltage from 1 kV to 220
kV and power up to 100 Mvar.
Metal Enclosed Capacitor Banks
ICAR proposes metal enclosed capacitors banks in many
different versions (fixed or automatic, with damping,
blocking and absorbtion reactors).
FIX CAPACITOR BANKS (WITH OR WITHOUT MAIN
BREAKER)
The fix banks are mainly adopted for the compensation
of steady loads or for fixed portions of the plant required
reactive power.
Typical example of the first case is compensation of large
MV motors, which are used for large pumping stations,
cement or chemical plants.
In this case the bank is placed close to the motor and it is
wired downstream its main Circuit Breaker, so it is switched
on and off along with its motor (for this connecting scheme
see Technical Remarks within this catalogue).
In the second case the capacitor bank is directly connect
to the distribution system bus bars.
Typical scheme of these capacitor banks is as follows:
Incoming Compartment can be equipped with options:
• Bus bars only and earthing switch (for the safety
earthing of the cap bank and so to make inspection
and maintenance
• inside the cell).
• no load line disconnector, earth switch;
• SPULKPZJVUULJ[VYVYÄ_LK*)"
• withdrawable CB;
Capacitor Step Compartment:
• Capacitors and Unbalance CT;
• Damping reactors, Capacitors and Unbalance CT;
• Blocking reactors, Capacitors and Unbalance CT;
AUTOMATIC CAPACITOR BANKS
These types of MV banks are normally divided in two or
three steps of regulation of the total reactive bank power
and they are operated automatically by a power factor
correction controller.
Each single step is switched by MV vacuum contactors.
Typical scheme of these capacitor banks is as follows:
Incoming Compartment can be equipped with options:
• bus bars only;
• no load line disconnector;
• SPULKPZJVUULJ[VYVYÄ_LKJPYJ\P[IYLHRLY"
• withdrawable circuit breaker;
Capacitor step compartment:
• MV vacuum contactor with HRC current limiting fuses;
• Damping or blocking reactors;
• Fast discharge resistors;
• Capacitors;
• Unbalance protection CT;
• Each step earthing switch.
In order to reduce dimensions of these banks, withdrawable
vacuum contactor solutions are also available.
These contactor metal clad cells are placed in the upper
part of the compartment.
This solution perfectly segregates the capacitor bank
compartment while the contactor is withdrawn, and it is so
possible to make step maintenance while the others are live.
As option, each capacitor bank step can be equipped with
a harmonic overload protection, which is made up of a high
current three phase relay integrated inside a multifunction
protection relay, along with unbalance protection function.
Automatic capacitor banks are available as standard for
power up to 5 MVAR and voltage up to 12 kV, both for indoor
and outdoor use, and steps from 500kvar to 2000 kvar.
For small power banks more essential solution may be
provided, such as a single compartment with Incoming
busbars, HRC current liming fuses, three phase delta
connection capacitors, earthing switch.
Fixed enclosed capacitor banks are available as standard
for power up to 5 MVAR and voltage up to 12 kV, both for
indoor and outdoor use.
14
Technical Remarks
VOLTAGE
Nominal voltage of a capacitor is the value of the alternating voltage for which the capacitor has been designed and that test voltage
are referred. The proper and safe use of power capacitors impose that working voltage does not overcome nominal voltage.
In special and particular conditions, capacitor units shall be suitable for operation at voltage levels according to table below (long
lasting voltage levels, extract of IEC 60871-1).
TYPE
Voltage Factor x Un
Max duration
Remarks
3BUFEGSFRV
1
Continue
/PNOLZ[H]LYHNL]HS\LK\YPUNHU`WLYPVKVMJHWHJP[VYLULYNPaH[PVU
3BUFEGSFRV
1.1
OL]LY`O
:`Z[LT]VS[HNLYLN\SH[PVUHUKÅ\J[\H[PVUZ
3BUFEGSFRV
1.15
TPUL]LY`O
:`Z[LT]VS[HNLYLN\SH[PVUHUKÅ\J[\H[PVUZ
3BUFEGSFRV
1.2
TPU
=VS[HNLYPZLH[SPNO[SVHK
3BUFEGSFRV
1.3
TPU
In any case capacitors and other power factor correction devices while they are working in overload leads to a reduction of their
expected life. Nominal voltage choice is then influenced by the following facts:
• 6UZVTLUL[^VYRZ^VYRPUN]VS[HNLJV\SKIL]LY`KPќLYLU[
• from nominal voltage
• Power factor correction equipment in parallel could cause an
• increase of the voltage at the connection point
• The voltage increases with the presence of harmonics on the
• UL[^VYRHUKVYJVZхVMPUHK]HUJLSLHKPUN
• Voltage at capacitor terminals is likely to be especially high
• Under low-load conditions.
When a capacitor is permanently connected to a
motor, difficulties may arise after disconnecting the
motor from the supply.
The motor, while still rotating, may act as a generator
by self-excitation and may give cause to voltages
considerably in excess of the system voltage. This,
however, can usually be prevented by ensuring
that the capacitor current is less than the no-load
magnetizing current of the motor; a value of about
90 % is suggested. As a precaution, live parts of a
motor to which a capacitor is permanently connected should not be handled before the motor stops.
WORKING TEMPERATURE
Working temperature of capacitor is a fundamental
parameter for safe operation. As a consequence it
is very important that heat generated is dissipated
correctly and that the ventilation is such that the heat
losses in the capacitors do not exceed the ambient
temperature limits. The capacitor temperature must
not exceed the temperature limits hereinafter tabled.
Ambient air temperature categories (60871-1) The
lower ambient air temperature at which the capacitor
may be operated should be chosen from the five
preferred values +5 -5 -25 -40 -50 °C.
AMBIENT TEMPERATURE °C
15
Symbol
Max value
A
Highest mean over any period of
24 h
1 year
40
30
20
B
45
35
25
$
50
40
30
D
55
45
35
Safety and Storage Instructions
CAPACITOR DISPOSAL
The capacitor and its impregnant oil should be disposed of in a manner consistent with the laws in force in the country where they
are installed.
Loss of the impregnant in the environment should be avoided or minimized. Consult the Material Safety Data Sheet for further
information.
SAFETY INSTRUCTIONS
Power must be switched off before doing any work on capacitors or equipments and accidental access has to be prevented.
To be certain that the capacitors have been disconnected from the power source, it is necessary to make a visual check for an
open-contact disconnect.
After being disconnected, the capacitors or equipment should then be shorted and grounded.
The capacitors have built-in discharge resistors which are designed to reduce the voltage, after the power is switched off, to 75 Vdc
or less in 10 minutes.
After the indicated time, the capacitors or equipment should be shorted and grounded by utilizing and insulated grounding stick or
equivalent and then the capacitor terminals should be connected together and to the case and grounded before handling.
Remove the shorting connection only just before the unit is reconnected in the circuit.
A failed capacitor should be handled very carefully.
It should be shorted with suitable insulated shorting sticks to discharge any residual charge.
Particular attention has to be paid to the internal pressure from
gassing, which is reduced if the capacitor is permitted to cool before
handling. In handling capacitors which have liquid leaking out, avoid
contact with the skin and prevent entry into sensitive areas such as
the eyes.
Close-fitting protecting gogglesshould be worn when handling units
which are leaking or might suddenly squirt impregnant while being
handled.
Contact with the skin is taken care of by simply washing off thoroughly
with soap and water as soon as possible.
The eyes can be quite irritated by the impragnant and so they should
be flushed with large amounts of water as soon as possible and the
examined by a physician.
STORAGE
Power must be switched off before doing any work on Capacitors
can be stored at temperatures between –40°C and +75°C and they
are not affected by humidity variation.
Take care of the terminals by protecting them against accidental
impacts which might damage them.
Shelter the capacitors from dust and aggressive or polluting
substances.
16
Icar Technical department is
ready to support customers in
design the most aproprieted
capacitor bank and harmonic
filters for their needs.
17
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